MERCK CHICKEN POX VARICELLA VACCINE PHASE III CLINICALS

MERCK CHICKEN POX VARICELLA VACCINE PHASE III CLINICALS demonstrated a protective efficacy rate of "at least 96%" for two seasons in 3,308 healthy children, Merck Director of Clinical Research Barbara Zajac, MD, told the Vaccines and Related Biologic Products Advisory Cmte. at its Jan. 24 meeting. Zajac said the seroconversion rate was "excellent, but not 100%." She added that 88% of nonresponders (12 children) seroconverted upon revaccination. Zajac also noted that there was no "evidence of transmission from 468 vaccinees to 446 siblings who received the placebo." The Merck vaccine was developed from the Oka strain, which the company licensed from Japan. Zajac concluded that the vaccine "in healthy children and adolescents is quite safe." She said the only significant post-vaccination reaction was mild rashes in 4% of the children. In follow-up of 11 children for four years, Merck found that antibody persisted, Zajac stated. An additional 350 leukemic children were also vaccinated with the vaccine. Merck exec Robert Gerety, MD, reported that extensive rash, with or without fever, has occurred in 16 of the children and the company has "temporarily suspended" the clinical vaccine program in leukemic children. He said Merck is "studying both the protocols that the children are on and the immune status of the children in whom the adverse reactions were seen." Merck and the Natl. Institute of Arthritis and Infectious Diseases are also sponsoring studies in which MMR II (measles, mumps, rubella) vaccine is given concomitantly with a varicella vaccine. Henry Balfour, MD, University of Minnesota, told the cmte. that in his experience with the quadrivalent immunization he has found "no excess of reaction" in 81 children administered MMR II and varicella vaccines simultaneously compared to 181 children administered varicella vaccine alone. Balfour noted that in the group receiving two vaccines there have been "more temperature elevations above 101 degrees Farenheit."